Abstract

21.1 Introduction

Relatively few works have been devoted to AB3 compounds as regards their hydrogen storage properties since the binary compounds exhibit rather low reversible capacities. However, new interests for this stoichiometry have appeared in the recent years with ternary systems A-Mg-Ni (A=Lanthanide, Ca, or Y) within the atomic composition 1:2:9. These compounds crystallize in an ordered variant of the PuNi3-type rhombohedral structure ( \( R\overline{3}m \) space group) and can be described as a stacking of AB5 (Haücke phase) and AB2 (Laves phase) units along the c axis.